1. Field of the Invention
The present invention relates to forms for molding columns and more particularly to a form for molding columns of any desired size, shape and surface design from solidifying materials such as concrete. The present invention also relates to a method for constructing the form.
2. Description of the Prior Art
Concrete columns are often used for support in buildings, bridges, and many other types of structures. These columns are generally formed by constructing a form or placing a preconstructed form in the desired location of the finished column, inserting metal rods or steel wire mesh in the form, pouring concrete into the form, and removing the form after the concrete has hardened. The metal rods and steel wire mesh are used to provide structural reinforcement for the column. However, such reinforcement is generally not needed if the column is molded around an I-beam.
The majority of concrete columns are molded by using spirally wrapped paper or cardboard tubes as forms. The resulting columns are of a uniform circular cross sectional shape. However, the paper tubes are not reusable because they are destroyed in the process of stripping them from the surface of the formed column. In addition, the paper tubes leave spiral relief marks on the column surface requiring additional labor to remove them. Furthermore, paper tubes cannot be used to mold a column around an I-beam unless the tube can be slipped over the I-beam.
Often concrete columns are molded by using a form constructed from wood. However, constructing wood forms is a labor intensive process. Also, due to the linear nature of wood, the forms and the resulting columns are generally rectangular. In addition, unless the wood is pretreated, the column will generally retain wood grain relief marks on its surface requiring additional labor to remove them.
Although circular or rectangular columns meet structural requirements, it is frequently desirable to provide concrete columns having other shapes and surface features for aesthetic effect. For example, it may be often desirable to create concrete columns that are oval, fluted, or have a brickwork surface.
U.S. Pat. No. 3,751,196 teaches an apparatus for manufacturing a concrete column form. The resulting manufactured form has a paper tube exterior for support and a polystyrene interior for forming a column with the desired size and cross-sectional shape. Columns with a multitude of cross-sectional shapes, such as oval, fluted, and polygonal, can be molded with a form created by this apparatus. However, this form cannot be used to mold a column around an I-beam unless the form can be slipped over the I-beam. In addition, this apparatus requires extensive set-up labor and materials for each size and shape of column to be formed.
Before manufacturing a form as taught by the aforementioned patent, a metal mandrel must be constructed with the same dimensions as the desired column. For example, if a fluted column is desired, then a fluted mandrel of the same dimensions must be constructed. If a second fluted column is desired with different dimensions such as diameter, then a second mandrel must be constructed. In addition, each mandrel must contain internal channels for allowing the flow of heating and cooling fluid or gas.
Once the mandrel is complete, it is inserted into an assembly for the manufacture of the form. The assembly holds the paper tube, lowers it over the mandrel, encloses the ends, then inserts an expandable plastic such as polystyrene beads into the enclosed space between the paper tube and the mandrel. A catalyst or other reactant is added, and the plastic is heated or cooled by fluid-filled channels. Once the plastic has hardened the mandrel is removed, thereby making the form ready for pouring of concrete or other material.
Although columns can be molded with forms constructed by this apparatus, the apparatus is cumbersome and limited. In addition to the expensive set-up required, the apparatus is limited to columns that have a uniform cross-section. That is, because of the process of pulling the mandrel from the molded plastic form, neither the form nor the mandrel can have horizontal relief patterns dependent on column height. For example, the apparatus cannot produce forms that would cast a column with a brickwork designed pattern surface pattern. If such a form were produced, the protruding simulated grout lines would be scrapped off the pattern by the mandrel during the process of removing the the mandrel from the form. Furthermore, these forms are not reusable because they are destroyed during removal from the cast column.